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Disposing of waste water poses a problem where sewerage networks are not available or composition of waste is complicated (agricultural and industrial). Many systems involve septic tanks and soakaways, but these are often out of date, overloaded or badly designed, so that they ultimately degrade the quality of the groundwater. This not only has negative environmental impacts, but puts further pressure on the limited water resources. Reed beds and constructed wetlands allow you to treat all your waste water on site and reuse it, a system which has become increasingly popular over the last 15 years. |
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What are reed beds and constructed wetlands? These systems utilise naturally occurring micro-organisms which break down waste. By providing an ideal environment for these microorganisms to thrive, it is possible to achieve a significant improvement in water quality within a relatively small area. These systems require no artificial additives and providing a suitable slope is available, need no power source. Maintenance is minimal and breakdown unlikely as there are almost no moving parts. The systems are robust and can handle variable inputs, making them ideal for use at sites with seasonal fluctuations. |
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The main types of system GreenWater constructs are:
Vertical Flow reed beds
Horizontal Flow reed beds
Combined Horizontal/Vertical flow beds
Waste water must first pass through a septic tank in order to remove solids. In many cases a septic tank is already present which overflows to a soakaway. This overflow effluent can then be harnessed and fed through the reed bed system for treatment, to be ultimately re-used as irrigation water or for other purposes such as water features. A typical domestic system could look something like the layout below.
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The vertical flow bed is effectively a gravel filled bath with the plug left out. Water enters the top of the bed amongst papyrus grass and trickles through the gravel where it passes aerobic bacterial communities. Once it reaches the bed base most of the suspended solids have been removed, the BOD content significantly reduced and nitrification occurred (the breaking down of ammonia to nitrates). The water is then collected by drainage pipes which lead to the horizontal bed. This is an anaerobic bed, comparable to a gravel bath with the plug left in. Water enters one end of the bed and moves through in a horizontal manner, effectively filling the bed and displacing all air, until it is allowed to escape at the far end. |
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The microbial fauna of this bed convert much of the nitrates to nitrites and nitrogen gas (denitrification) and consume any pathogens in the water. From there on the water may be used for a variety of purposes having achieved the desired levels of purity. Depending on the site this may be for irrigation, plumbed back through the system or discharged to a water course. So…does it really work? Analysis of reed bed treated effluent shows significant reduction of all contaminants to a level well within the acceptable limits i.e. a level which poses no harm to any of the users. Providing construction, operation and maintenance are carried out to the specific design then this system will work in nearly all sites. |
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See GreenWater clients >> |
Doesn't it
smell?
This is the most common of concerns about treating waste water, as well as the whole issue of dealing with it on site. However, most of the water within the gravel beds is below the surface, meaning that it is possible for people to be peacefully sipping their tea only metres from a bed and not even realise what is going on right next to them (such is the case with a system at a British hotel). Maintenance is minimal so the system really is unobtrusive in many ways. Additionally, due to the presence of wetland plants a whole host of birds, insects, amphibians and other animals will be attracted to the site, creating a lively ecosystem and generating interest with visitors. Reed beds have a relatively small footprint as they are altering waste water disposal habits. By creating water to re-use on a site, overall water consumption is lower and groundwater protected from soakaway pits. |
